JPS62240811A - Traveling direction detector for vehicle - Google Patents

Abstract

PURPOSE:To enable the accurate detection of the traveling direction immediately after the start of running, not being affected by an error in mounting, by computing the turning radius of a vehicle on the basis of the difference in the speed of rotation between two wheels which is caused by a steering operation, and by calculating a steering angle therefrom. CONSTITUTION:Running distance sensors 20 and 21 are formed of magnets connected to left and right rear wheels 12 and 13 respectively and of lead switches operated thereby in an ON-OFF manner, and deliver output pulses every time the rear wheels 12 and 13 rotate by a unit angle. These output pulses are inputted to CPU 23, and the respective speed of rotation of the rear wheels 12 and 13 is calculated from an output pulse per unit time and stored in RAM 25. The turning radius R is computed from the difference in the speed of rotation between them, and the direction of turning of the vehicle is determined therefrom. Although there is scarcely any difference in the speed of rotation between the rear wheels 12 and 13 in the state of straight running of the vehicle, the speed of rotation of the rear wheel 13 becomes larger than that of the rear wheel 13, for instance, when the vehicle is turned to the right. Then the absolute value of the turning radius R becomes a value corresponding to the inverse number of the difference in the speed of rotation, the sign thereof turns to be plus, and a steering angle turns to be proportional to 1/R.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a device for detecting the traveling direction of a vehicle.

<Prior art> In general, the so-called absolute angle detection method, which uses a potentiometer or the like to extract a voltage signal according to the steering angle, has been used to detect the steering angle as the direction of travel of the vehicle, and a photo sensor. There is a so-called relative angle detection method that sends out a pulse every unit angle rotation of the handle.

<Problems to be solved by the invention> However, in the former absolute angle detection method, the correspondence between the zero point of the potentiometer, etc. and the straight direction of the car is done on the car assembly line, so it is impossible to completely match this. It is difficult to do so, and some installation errors are unavoidable.

Therefore, it is necessary to adjust the zero point, but this adjustment is troublesome and there is a problem that the zero point changes with aging.

In addition, in the latter relative angle detection method, since the neutral position (straight ahead) when the power is turned on is not known, it is necessary to calculate the neutral position by software processing based on the tendency of the car's driving condition. If not, there is a problem in that it is not possible to detect the neutral position, and furthermore, it is not possible to accurately detect the steering angle.

<Means for Solving the Problems> The present invention has been made to solve the above-mentioned conventional problems, and its gist is to detect the rotational speeds of the two left and right wheels or the two front and rear wheels. The vehicle is equipped with wheel speed detection means for calculating the turning radius of the vehicle based on the speed difference between these two wheels.

Effect> With the above configuration, when a difference occurs in the rotation speeds of the two wheels due to the steering operation, the turning radius of the vehicle is calculated based on the speed difference, and the steering angle can be calculated.

<Example> Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a diagram illustrating the principle of the present invention, and shows the motion of the wheels when a car turns.

In the figure, 10.11 indicates the left and right front wheels, 12.
13 indicates the left and right rear wheels. Now, if we consider a situation in which the front wheels 10.11 are turned as shown in the figure by the steering operation and the car is running, the running trajectory of the rear wheels 12 and 13 is an arc 12a, 13a centered on the turning center 0 of the car. Therefore, they move with different radii of curvature.

Here, the distance between both rear wheels 12.13 is a, and both rear wheels 12
．． 13, the turning radius R1 of the right rear wheel 12 and the turning radius R2 of the left rear wheel 13 are expressed by the following formula (11, (2)), and the turning radius per unit traveling angle θ is expressed by the following formula (11, (2)). Traveling amount of both rear wheels 12.13!!1.z2 is the following formula (
3), +4).

R1=R----・-(1) R2=R+-・-・(2) dJ1=R1dθ −・−(3) d12=R2dθ −(4) From these formulas, the turning radius R at the intermediate point is, Also, the travel distance 11,122 is the rear wheel 12°13
The turning radius R can also be expressed as follows.

Therefore, the turning radius R of the car can be determined based on the relative speed difference between the rotational speeds Vl and V2 of the rear wheels 12.13, and this turning radius R is proportional to the turning angle of the car and, in turn, to the steering angle. becomes.

Next, a specific example of detecting the turning angle of a vehicle based on the above-described principle will be described.

In FIG. 2, 20 is a mileage sensor that detects the mileage of the right rear wheel 12, and 21 is a mileage sensor that detects the mileage of the left rear wheel 13.
, 21 are formed by magnets connected to the left and right rear wheels 12.13, respectively, and reed switches that are turned on and off by the magnets.
An output pulse is sent out every time the eye position angle of the eye is rotated.

23 is the central processing unit (CPU) of the microcomputer
, 24 is a read-only memory that stores fixed programs.
(ROM), 25 is rewritable memory (RAM)
shows.

The output pulses from the mileage sensors 20 and 21 are CP
The CPU 23 counts the output pulses per unit time and calculates the rotational speed V of both rear wheels 12.13.
1 and V2 are calculated and stored in RAM2S.

In the above configuration, the process of detecting the traveling direction of the car is performed in the third
This will be explained based on the flowchart shown in the figure.

First, in step 30, the rotational speeds Vl and V2 of both rear wheels 12.13 stored in the RAM 25 are read, and in step 31, the turning radius R is calculated based on the difference between these rotational speeds Vl and V2. At 32, the turning direction of the vehicle is determined. This turning direction is
The turning radius R is determined based on whether it is larger or smaller than O, and if the turning radius R is infinite (2), it is determined that the vehicle is traveling straight.

That is, when the car is running straight, the left and right rear wheels 12
．． 13, there is almost no difference in rotational speed, and the turning radius R at this time
is infinite, but when the car is turned, for example, to the right by steering wheel operation, the rotational speed V2 of the left rear wheel 13 becomes larger than the rotational speed v1 of the right rear wheel 12, and the absolute value of the turning radius R becomes The value corresponds to the reciprocal of the rotational speed difference, and its sign is 10. As a result, the car turns to the right, and the steering angle becomes proportional to 1/R.

In the above embodiment, the turning radius of the car is detected based on the speed difference between the left and right rear wheels, but the two wheels to be compared may be the left and right front wheels, or the front and rear wheels. In short, it is sufficient as long as it produces a speed difference when the car turns.

In addition to finding the wheel speed as the distance traveled per unit time, it can also be determined by converting the frequency of the output pulse from the distance sensor into voltage using an F/V converter.

<Effects of the Invention> As described above, the present invention is configured to detect the turning radius of the vehicle based on the speed difference between the left and right wheels or the front and rear wheels, so it is not affected by installation errors as in the past. (Moreover, even after the vehicle has started driving, it has the effect of being able to accurately detect the direction of travel as soon as the vehicle turns.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; FIG. 1 is a diagram showing a turning state of a vehicle for explaining the present invention, FIG. 2 is a control block diagram, and FIG. 3 is a flow chart. 10-13... Wheels, 20.21... Travel distance sensor, R... Turning radius.

Claims (1)

[Claims] (1) Equipped with wheel speed detection means that detects the rotational speed of the two left and right wheels or the two front and rear wheels, and turning radius calculation means that calculates the turning radius of the vehicle based on the speed difference between these two wheels. A device that detects the direction of travel of a car.